1. Field
The disclosed concept relates generally to machinery and, more particularly, to machines, such as for example, machines used to apply and/or repair coatings used on can ends in the food and beverage packaging industries. The disclosed concept further relates to spray assemblies and spray heads.
2. Background Information
Typically, can bodies for food or other products are provided with easy open can ends that are characterized by having a pull tab attached to the can end, which is used to fracture a tear panel on the can end defined by a score line on the can end. For example, the pull tab may be lifted to depress the tear panel in order to provide an opening in the can end for dispensing the contents of the container.
Likewise, many food products are sold in can bodies provided with full open easy open can ends that are characterized by having a pull tab attached to the can end, which is used to fracture a score line that circumscribes the circumference of the end panel to define an opening panel. For example, the pull tab may be lifted to fracture the score line. After the score line is fractured, the pull tab may be pulled upward from the container to sever the remainder of the score line in order to remove the entire opening panel for dispensing the contents of the container.
In the manufacture of an easy open can end, a pre-converted can end, commonly referred to as a shell, is conveyed to a conversion press. In the typical operation of a conversion press, the shell is introduced between upper and lower tool members, which are in the open, spaced apart position. A press ram advances the upper tool member toward the lower tool member in order to perform any of a variety of tooling operations such as rivet forming, paneling, scoring, embossing, and final staking After performing a tooling operation, the press ram retracts until the upper tool member and lower tool member are once again in the open, spaced apart position. The partially converted shell is then transported to the next successive tooling operation until an easy open can end is completely formed and discharged from the press. As one shell leaves a given tooling operation, another shell is introduced to the vacated operation, thus continuously repeating the entire easy open can end manufacturing process. Examples of easy open can ends can be found, for example, in U.S. Pat. Nos. 4,465,204 and 4,530,631. Conversion presses can operate at speeds that manufacture in excess of 500 can ends per minute per lane, with some presses having four lanes of tooling thereby manufacturing up to 2000 converted can ends, or more per minute.
Steel sheet stock used in the manufacture of can ends has a coating that protects the metal by inhibiting oxidation, corrosion or rust from forming on the surface of the metal. During the conversion process, damage to the protective coating typically occurs while forming the score line that defines the tear panel or opening panel of the can end. As noted above, in the conversion of a shell into a can end with openable features thereon, tooling is employed to form the aforementioned score line. The score line is the most likely location where damage is caused to the protective coating. Any oxidation, corrosion or rust on the surface of the can end that could result from such damage to the protective coating represents an unattractive product appearance to the consumer and is generally unacceptable to canmakers. Accordingly, as a precautionary measure to prevent oxidation, corrosion or rust from appearing on the can end, many canmakers apply a fluid, repair agent, lacquer or paint to coat the scored area of the can end by spraying the can end. This process is generally referred to as score repair or post repair.
The spray heads for known spraying apparatus and methods for score repair typically employ a single spray gun, which is rotated at relatively high speed (e.g., about 1000 rpm) in order to enable the spray gun to make one complete revolution around the can end during the spray portion of the machine cycle. Commonly assigned U.S. Pat. No. 7,622,002 discloses a spray machine, which employs a low-pressure solid stream spray head and method to reduce over spray or spray beyond the scored surface of the can end, and allow for improved machine efficiencies, for example, due to reduced downtime associated with routine cleaning and maintenance.
There is room for improvement in post repair machines, and in spray assemblies and spray heads therefor.